1. Field of the Invention
The present invention relates to an information memory apparatus and, more particularly, to an information memory apparatus having a plurality of disk drives.
2. Description of the Related Art
Memories have been studied and developed enormously to achieve a large storage capacity and a high processing speed. For example, as disclosed in NIKKEI ELECTRONICS, Apr. 26, pp. 77-103, 1993, a great deal of attention has been paid to a technique of achieving high performance and high reliability by arranging a magnetic memory and the like for parallel processing. Such a system has been put into practice. Since this system basically uses a fixed disk (unportable disk) unit as an information storage medium, the storage capacity of the system is limited by the size of hardware prepared in advance. For this reason, as disclosed in NIKKEI ELECTRONICS, Sep. 15, pp. 153-160, 1991, if a request is generated to store data exceeding the storage capacity of a system, unnecessary data are erased, or data exhibiting low access request levels are backed up to a portable medium such as a floppy disk, thereby setting a free area in a fixed disk unit.
As described above, in a system based on a fixed disk unit such as a hard disk unit, the storage capacity is limited by the size of hardware. If both a fixed disk and portable disks are used, the system cost increases, and the operation of the system is complicated, making it difficult to use the system.